|
This is an excellent question - the bad news is, the answer is rather complicated. You would need to implement a unification algorithm[^] to do it correctly.
Things would not be as bad if you considered Prolog[^] as the language for your implementation, but something tells me that that would be out of the question 
On the other hand, you can always embed Prolog to get unification for free.
But no matter how you look at it, the learning curve is going to be steep.
Good luck!
|
|
|
|
|
That page only seems to discuss logic formula's (unless I'm missing something?), does it also work for other formula's?
|
|
|
|
|
Absolutely. Formally, you can represent A+B as add(A,B), and define an additional rule that add(A,B) :== add(B,A). In fact, since you are interested only in a yes/no answer (as opposed to variable assignments produced by unification), you don't even need to implement a complete unification: a simpler recursive matching algorithm would do. The only challenge in its implementation is matching ((A+B)+C) trees to (A+(B+C)). You can deal with it by flattening the list of operands, and trying all possible orderings on one of the sides. Don't forget to memoize[^] your matches, both positive and negative. Otherwise, your search will be too slow.
|
|
|
|
|
java or C# , which better?
|
|
|
|
|
I would personally prefer C#.
|
|
|
|
|
As far as algorithms go, they are equal.
"You get that on the big jobs."
|
|
|
|
|
Actually, I wouldn't say that.
What is the algorithm for 64bit unsigned division in Java?
|
|
|
|
|
For a Java-programmer, Java is better. For a C# programmer, C# is better. Try to find where they differ, as that decides which of the two is best for the given circumstance.
I are Troll 
|
|
|
|
|
COBOL 
Regards
David R
---------------------------------------------------------------
"Every program eventually becomes rococo, and then rubble." - Alan Perlis
The only valid measurement of code quality: WTFs/minute.
|
|
|
|
|
|
Even better - I once spent 6 months doing MUMPS. DOn't think I've recovered. 
Regards
David R
---------------------------------------------------------------
"Every program eventually becomes rococo, and then rubble." - Alan Perlis
The only valid measurement of code quality: WTFs/minute.
|
|
|
|
|
Strange, I had Mumps when I was a boy and recovered after a couple of weeks.
I must get a clever new signature for 2011.
|
|
|
|
|
Look at the IDE which is available for the language. As both with Java and C# you can create nice programs, the IDE is important. And I prefer Visual Studio.
|
|
|
|
|
Neither: they are just different. Some problems may be solved easier in one language, but that does not make it better than the other. Every language has its fans, detractors and bigots. I would just use the language that you feel most comfortable with, whatever it may be.
I must get a clever new signature for 2011.
|
|
|
|
|
None of them, and both of them. A better question would be: which language is better for doing -whatever-?
|
|
|
|
|
C# is better, in my biased opinion. It started out as what looked like a Microsoft attempt to copy Java, but it's evolved into much more than that.
The later versions of C# have eliminated a lot of the bloat of previous languages, allowing succinct expression of programming ideas in code. This leads to greater clarity, which makes code more reliable and maintainable.
|
|
|
|
|
without context, without goals, this is a stupid question.
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
|
|
|
|
|
After reading the book Pro C # and. Net 4
I discovered the enormous benefits offered by C # compared with Java 
There are many differences: LINQ , WPF , WCF
Today, I like C# 
|
|
|
|
|
yeah I agree... C# has alot more to offer than Java.
"Program testing can be used to show the presence of bugs, but never to show their absence."
<< please vote!! >>
|
|
|
|
|
Well I've googled it and came across a wiki page of the differences...
All and all the conclution that I could make out was that C# had most of the features that java had and much more.
"Program testing can be used to show the presence of bugs, but never to show their absence."
<< please vote!! >>
|
|
|
|
|
hello
i have a file with only entry of 0..9 (numbers only) without any other thing even space , what is the most efficient algorithm to compress it?
thanks in advance.
|
|
|
|
|
at the command level, use a ZIP utility, such as WinZip.
When programming an application, create a binary file. Assuming all digit values have same probability, you could:
- create a binary file with BinaryWriter class; it will be filled with ulong values;
- the first value to write would be the number of digits to be stored;
- then have a loop that reads 19 digits, turns them into a single ulong (use ulong.Parse or TryParse), and outputs that ulong in binary;
- when reaching the end of the input data, which probably did not have a length evenly divisible by 19, just imagine the few missing digits are all zero, and generate the last ulong as you did all the others.
That is it; you have turned N characters (probably bytes in an ASCII text file) into a sequence of N/19*8 bytes, giving a compression factor of 2.37
You could do better if something was known about the distribution of the digits; otherwise that is about the best you could get.
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
|
|
|
|
|
No, a compression factor of 2.37 for that purpose is not good at all. Just send a text file to a "zip compressed" folder in Windows explorer, and you get a compression ratio of about 10. And, of course, the text file contains not only digits but other ASCII characters also, which means that it already contains much more information per byte of storage, than does the file with digits only.
Hence I'd take some common zip algorithm. The "ICSharpZipLib" is also available for commercial products (see http://www.sharpdevelop.net/OpenSource/SharpZipLib/[^]).
In the Unix world, I sometimes see "bz2" compressed files which are said to be extremely compressed; but I do not know a library to handle that with .NET.
|
|
|
|
|
Incorrect. You either believe in magic, or you didn't understand my suggestion.
So I created a little proof:
public void generateFiles() {
using (TextWriter tw=File.CreateText("test.txt")) {
using (BinaryWriter bw=new BinaryWriter(File.Create("test.dat"))) {
int DIM=100*1000;
Random r=new Random();
for (int i=0; i<DIM; i++) {
ulong n=0;
for (int j=0; j<19; j++) {
int d=r.Next(10);
tw.Write("01234567890".Substring(d,1));
n=10*n+(ulong)d;
}
bw.Write(n);
}
}
}
}
and I WinZipped the txt file; the resulting sizes were:
.txt = 1,856 KB
.dat = 782 KB (that is a compression factor of 2.37 indeed)
.zip = 872 KB (that is 2.13)
which tells me WinZip is wasting around 10%.
While ZIP normally achieves around a factor of 10, that simply can not be achieved when the data is really random and has log2(10) significant bits in each 8-bit byte (if it could, it would store a digit in less than one bit which is clearly impossible)
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
|
|
|
|
|
That is, the high compression rate of Windows zip with texts like log files is caused by the repetitive structure of the contents, though some 6 out of 8 bits per byte are used for the text.
With log2(10) significant bits per byte, the theoretical limit should then be a compression factor of 2.408, thus your idea already achieves some 98.5% of it.
Let's see how much more number crunching and execution time will be required to get it one percent better.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
